Method of making sulphur trioxide



Patented Dec. 26, 1933 r I f1,941,4g7; V

' METHOD or MAKING sunrnoarmoxmn Alling P, Beardsley, Plainfieldf'N; J.,

and

Napoleon Arthur Laury,- Rockville Center, ;N. Y., assignors to The Calco Chemical Company, Inc.,'Bound Brook,-,N. J.,'-a corporation of Delaware No Drawing; ,Appucatnn'my 13, 1929 SeriaLNo. 362,882

.14 Claims; (CL 23-175) This invention relates to a method of making sulphur trioxide and to a catalyst for use insaid method.

In making sulphuric acid by the contact method, it is customary to bring sulphur dioxideand oxygen into contact with a catalyst at an elevated temperature. While the most common catalyst for this :purposeis platinum, the catalytic action of vanadium in thisprocesshas long been recognized, and vanadiumghas .tosome extent been usedias a catalyst in carrying out the method commercially. a .We have discovered that the catalytic action of vanadium in causing areaction between'sulphur dioxide gas and oxygen is greatly increased by the presence of the rare element rubidium, and that rubidium acts as a promoter to the catalytic action. of variadium,-and serves both toincrease the catalytic action throughout the temperature 29 rangeat which vanadium acts as a catalyst in this reaction and to extend this temperature rangedownward to a material extent.

, Our invention, which is based on this discovery, consists in improving the contact method of making sulphuric acid, by, usingga vanadium catalyst with rubidium as a promoter and in a vanadium and rubidium catalyst-for use in said.

method.

While catalytic masses embodying'the invention may be made in numerous different ways, we will, for the sake of illustration, describe a specific method for making such a mass which we have found satisfactory and effective in practice:

An aqueous solution of ammonium meta-vanadate (NH4V03) is prepared. In this solution is immersed a porous carrier, such as celite (tradename applied to diatomite or diatomaceous earth sold by the Johns-Manville Corp., of. 292 Madison Ave, N. Y. C.) chips calcined at about 1000 C. When the carrier has absorbed the solution to saturation, it is removed and dried at 110 C. It is then again immersed in the solution and dried, and the process is repeated till all the solution has been absorbed in the carrier. An aqueous solution of rubidium ch10:- ride (RbCl) is then applied to the carrier by sprinkling. chloride, the carrier is dried at 110 C.

We have found that'the actionof rubidium as ,a promoter to the catalytic action of vanadium shows material increase with an increase in the proportion of rubidium present up to the point.

at which the amount ofrubidium in the mass is, atomically, three times that of the vanadium.

After saturation with rubidium;

,The proportion of the rubidium mayibe varied within this limit to satisfy conditions of use in which the maximum promotionis unnecessary.

;A desirabl e composition forcommercial purposes is one in: which the amounts of vanadium and rubidium are approximately. atomically equal. To prepare sucha mass by-the above method,.the

proportions ofthe soluble salts. and the carrier:

used are as follows:; H

Ammonium meta-vanadate n one part by weight Rubidium -chloride one part by weight Carrier (calcined celite) 6.3 parts by weight It is desirable, though not essential, to heat the impregnated carrier up to about 500? C.

in anatmosphere; containing S02 before v themass. v

V In the manufacture of sulphuric acid inaccordancewith our invention, a mixture containing oxygen and-sulphur dioxide gases is passed through a converter chargediwith the contact mass above described. ;The heat evolved byfthe combination of .the gases coming in contact with the catalyst issystematically removed during-the passage of the-gases throughthe'converter, so that the temperature of thfigas in contact with the catalyst :is reduced to. a temperature of about 420 C. as it leaves the catalyst, material conversion taking place at the lower'temperature,

and affording a total conversion of 98%.

Comparative tests of the catalytic mass above described and a vanadium contact mass precisely similar in all respects with the mass described, except for the omission of the rubidium, show that at all temperatures, from 375 C. to 500 0., the percentage of conversion of S02 and, 0 into S03 is materially increased by the presence of the rubidium, and that particularly at; temperatures below 450 C. at which little conversion is obtained by the mass containing vanadium only,

very material conversion is obtained by the mass containing vanadium and 'rubidium.

.Our invention is by no means limited to a catalytic mass prepared in accordance with'the specific method which has been given as an illus- 'tration. This method may readily bemodified by the substitution of chemical equivalents, such as the use of other soluble vanadium'compounds, I

instead of the ammonium 'meta-vanadate. Fur-. thermore; although we have found that an ad- 'as a chloride or other neutral salt of a mineral vantage is gained by introducing the rubidium acid, it is nevertheless true that satisfactory conversion may be obtained. if other soluble rubidigood results.

um compounds are substituted for such salts. Furthermore, it is not essential to apply the vanadium solution and the rubidium solution to the carrier separately. The solutionsmay be mixed before application to the carrier, or a single solution of a single soluble salt, such as rubidium-vanadate (RbVOs) may be used with taining vanadium and rubidium in the claims which follow should, therefore, be-understood to include a single solution-oi a singlesalt, except where separate solutionsare expressly specified.

What is claimed is:

1. A catalyst for use in the contact methodof making sulphuric acid, comprising vanadium and rubidium, in which the gram-atoms of rubidium are less than four times the gram-atoms of vanadium.

2. A catalyst for use in the contact method of, makingsulphuric acid, comprising vanadium and rubidium, in Whichihe gram-atoms of "rubidium are approximately equal to the gramatoms of vanadium.

, 3. Acatalytic mass for use in the contact method'of making sulphuric acid, comprising a porous carrier, and vanadium and rubidium on the surface and in the pores of said carrier.

'4. A catalytic mass for use in the contact method of making sulphuric acid, comprising porous particles of substantially pure silica, and

vanadium and rubidium on the surface and in the pores of said particles. J V

5 A catalytic mass for use in the contact method of making sulphuric acid, comprising a porous carrier of the type of calcined diatomite,

The references to solutions con--- which has been heated after impregnation, and previous to use, in an atmosphere containing sulphur dioxide.

-8. A catalytic mass. for use in the contact method of making; sulphuric acid, comprising a porous carrier of calcined diatomite, which has been impregnated with a vanadate solution and a separate solution containing rubidium, and which has been heated after impregnation, and previous to use, in an atmosphere containing sulphur dioxide.

'9. A catalyticmass for use in the contact method of making sulphuric acid, comprising a silica carrier which has been impregnated with a vanadium solution and a solution of a neutral rubidium salt of a mineral acid.

lO..A catalytic mass for use in the contact method of making sulphuric acid, comprising a silica carrier which has been impregnated with a vanadium solution anda solution of rubidium chloride.

11. The method of making sulphur trioxide, which consists in passing a mixture of gases containing oxygen and sulphur dioxide at an elewhich consists of porous particles of substantially pure silica impregnated with solutions contain ing vanadium and rubidium.

12. The method of 'making sulphur tri'oxide,

which consists in passing a mixture of gases con taining oxygen and'sulphur'dioxide at an elevated temperature through a catalytic mass consisting of a porous carrier carrying vanadium and rubidium, and in reducing the temperature of the gases so that as they leave the mass they to eachothenthe catalyst being deposited upon an inert carrier.

vated temperature through a catalytic mass 1 14. A catalyst for use in the contact method 

